In a radio network, a Random Access CHannel (RACH) is used as the common entrance for all devices which request a dedicated communication channel. This includes devices which are accessing the network for the first time as well as those which have already been using the radio network but have temporarily lost their synchronization towards the radio network. A first message exchange is carried out between the device and a base station/access point of the radio network, and in particular over the Physical RACH (PRACH) where the bandwidth of an uplink (direction from the device to the base station) is very limited. In an “attach storm” scenario, this may cause heavy load on the RACH as well as on the base station/access point itself. A malicious or malfunctioning device could bypass existing procedures and cause a denial-of-service attack by exhausting channel resources and/or processing resources, by just overusing the existing attachment procedure. Such attach storms may also occur naturally, e.g. when thousands of devices located in a dense “hot spot” attempt to reconnect after a temporary outage.
Making radio network services unavailable for its subscribing users e.g. by such attach storms obviously causes dissatisfaction among the users, and should be prevented. Increasing the radio resources is not a feasible solution e.g. in view of the scarce nature thereof, nor is adding processing capacity to the base stations as this is an expensive solution.
In such overload or attach storm situation it would however still be desirable to allow e.g. devices that are or have been connected to the radio network but temporarily lost synchronization, a faster access to the radio network than those devices which have not yet connected to or established network services. The former type of devices may have ongoing conversation or data transfer and a fast reconnection might reduce user dissatisfaction.